JPH0449775A - Color picture processor - Google Patents

Abstract

PURPOSE:To improve picture quality by dividing an input picture into plural areas and selecting an optimum masking coefficient based on a weighted result. CONSTITUTION:First color picture data RGB are divided into plural areas by an area dividing part 1 and the weighting of the respective areas is executed by a weighting part 2. A masking coefficient storing part 5 stores plural making coefficients to correspond to the hue of a picture, the hue represented for the whole picture is found based on the result of the weighting by the weighting part 2 and the making coefficient to correspond to the hue is selected from the storing part 5. A masking converting part 6 executes the masking converting of the whole input picture by the masking coefficient selected by a masking coefficient selecting part 4 and generates output picture data CYM which is a second picture data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image processing device for a digital color copying machine, a color printer, etc., and particularly relates to a color image processing device for a digital color copying machine, a color printer, etc. The present invention relates to a color image processing device that generates output signals of three primary colors.

[Prior Art] For example, when reading a document image in a digital color copying machine, the reflected light of the document image is divided into three primary colors of light, red (R), green (G), and blue (B), by an optical filter. The colors are separated into two, and both image impressions are input for each basic color. On the other hand, when outputting, subtractive color cyan (C) is used.
A wide variety of colors are reproduced by combining the three primary colors: , magenta (M), and yellow (Y).

For this reason, in the color copying machine mentioned above, it is necessary to convert R, G, and B image data obtained from the input system into C, M, and Y image data for the output system. This is done by a method called masking correction, and the operational determinant for this purpose is called a masking matrix, and the matrix coefficients are called masking coefficients.

By the way, in order to perform appropriate color correction by converting the image data, it is necessary to select masking coefficients that are suitable for the input image. Therefore, masking coefficients are usually selected such that the color difference between the input image and the output image is uniform throughout.

[Problem to be solved by the invention]

However, for example, it is necessary to take in an image such as a landscape photograph containing people from an input system, faithfully reproduce it, and output it.
If you try to do so, the output may be an image that gives a diffuse impression, with neither the person nor the background having focused color points. This is because the above-mentioned input image often has a wide distribution in the color region in all directions of brightness, saturation, and hue, and the accuracy of color reproducibility varies locally. To prevent this, it is possible to partially change the masking coefficient.
There is a problem that the processing time becomes long.

The present invention has been made in view of the above circumstances, and by selecting the optimal masking coefficient for the most noteworthy part of the horn image and improving the accuracy of color reproducibility of the part of interest, The object of the present invention is to provide a color image processing device capable of outputting a color image that gives a visually pleasing impression.

[Means to solve the problem]

A color image processing device according to the present invention converts first color image data represented by three additive primary colors into second color image data represented by three subtractive primary colors using a masking coefficient. , a dividing means for dividing the first color image data into a plurality of regions, a weighting means for weighting each region divided by the dividing means, and a plurality of masking coefficients corresponding to the hue of the image are stored. and means for determining a hue representative of the entire image based on the weighting result by the weighting means and selecting a corresponding masking coefficient from the storage means.

[Effect]

The first color image data is divided into a plurality of regions by the dividing means, and the weight of each region (\1
Muj is held. The storage means stores a plurality of masking coefficients corresponding to the hue of the image, a hue representative of the entire image is determined based on the weighting result by the weighting means, and a masking coefficient corresponding to this hue is selected from the storage means. be done.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a block diagram showing the configuration of a color image processing apparatus according to the present invention. In the figure, reference numeral 1 denotes an area dividing unit that divides the original image into a plurality of areas, and input image data RGB, which is first image data, is input to this area dividing unit 1. This input image data RGB has been converted to data in an RGB color space of eight hue directions, including brightness and saturation. The image data divided by the region dividing section 1 is given to the weighting section 2, which weights the divided regions as will be described later, and gives the result to the attention region determining section 3. The attention area determination unit 3 determines the area that attracts the most attention based on the weighting results, and uses the result as a masking coefficient selection unit 4.
humiliate The masking coefficient storage unit 5 stores a plurality of optimal masking coefficients corresponding to various hues, and the masking coefficient selection unit 4 stores optimal masking coefficients corresponding to the hue of the attention area determined by the attention area determination unit 3. is selected from the masking storage section 5. The masking conversion unit 6 performs masking storage for the entire human image using the masking coefficient selected by the masking coefficient selection unit 4, and generates output image data CYM as second image data.

Next, a procedure for processing image data by the apparatus of the present invention configured as described in 1- below will be explained using the flowchart shown in FIG.

First, in step 1, an input image is divided into a plurality of regions. FIG. 2 is a diagram showing an example of the divided regions, in which the input image is divided into 25 regions. In the next step 2, the divided regions are weighted. For example, there are three methods for this weighting as shown below.

■ Weighting by location When looking at an image for the first time, the center is usually the center of attention. For this reason, the central portion is weighted the highest. In other words,
In the example of FIG. 2, the degree of weighting of region 13 is the highest,
The surrounding area 7, 8. 9. 12. 14° 1? , 18
．． 19 to the middle, and the surrounding area 1, 2, 3° 4
．． 5, 6.10.11, 15.16.20.21.22
．． 23.24.25 can be set as the lowest.

■ Weighting based on density (brightness) Normally, humans have a higher ability to distinguish bright areas than dark areas, and by emphasizing bright areas, it is possible to create a beautiful impression. As a result, it is possible to set the degree of weighting to be the highest for low-density, ie, bright, areas, to the medium for medium-density areas, and to the lowest for high-density, ie, dark areas.

■ Weighting by hue Normally, humans tend to closely observe skin color, so
The degree of weighting can be set to the highest for the region including this, to the medium for the region including the green of trees or the blue of the sky, and to the lowest for the other regions.

As described above, weighting (=j) of the region is performed based on each viewpoint, and from this result, the region of interest is determined in step 3. For example, if weighting is performed using each of the three methods described above, Three weightings are set.Thus, by adding these weights for each area, the area with the highest weighting among all areas can be determined as the area of interest.For example, a person is placed in the center in front light. In the case of a captured photographic image, the central area where the person is placed is determined as the area that attracts the most attention.

In step 4, a masking coefficient optimal for the hue of the negative region of interest determined in step 3 is selected from the masking coefficient storage unit 5. Then, in step 5, masking conversion is performed using the selected masking coefficients, and the output image data C
Generate YM.

〔effect〕

As described above, in the color image processing device according to the present invention, the input image is divided into a plurality of regions and the optimal masking coefficient is selected based on the weighted results. The accuracy of color conversion and reproducibility of areas with strong color is improved, and it is possible to output a color image that gives a favorable impression. In other words, since color conversion and reproducibility of areas other than the focused area do not require much visual accuracy in the entire image, it is possible to take advantage of the time efficiency of color conversion of the entire image using one masking coefficient. The present invention has excellent effects such as being able to obtain good images.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a color image processing apparatus according to the present invention, FIG. 2 is a diagram showing divided regions, and FIG. 3 is a flow chart showing the procedure of image processing.

Claims (1)

[Claims] 1. A color image processing device that converts first color image data represented by three additive primary colors into second color image data represented by three subtractive primary colors using a masking coefficient, comprising: a dividing means for dividing one color image data into a plurality of regions; a weighting means for weighting each region divided by the dividing means; and a memory storing a plurality of masking coefficients corresponding to the hue of the image. A color image processing apparatus comprising: means for determining a hue representative of the entire image based on the weighting result by the weighting means, and selecting a corresponding masking coefficient from the storage means.